There is a growing trend for libraries, universities and other institutions to archive digital images of rare and fragile books in the event that damage or deterioration occurs to the original, or in view of making available their content to a large public, on a specific web-site for instance.
One conventional method for imaging a page of a book consists in taking a picture of the page with a scanner. In this method, the book is lying flat inside the scanner to avoid distortion of the captured images. The major problem with this imaging method is the difficulty to open the book to 180°, due to the binding. Thus, this method may lead to irreversible damages to books which have fragile bindings, and for books which can not be fully opened, if one attempts to wide open the book. Therefore, this method is inappropriate for old books which are generally opened to 120° or less to minimize stresses on the book binding. Another problem of this method is the risk of a deterioration of the pages of the book due to the contact between said pages and the transparent plate of the scanner.
One known solution to these problems is the use of specific optical devices permitting the imaging of partially open books. in particular, EP 0 655 855 A2 relates to such an optical device. In this prior art, the solution consists to employ a wedge scanner comprising 2-dimensional array detectors attached at a common edge and disposed in a wedge shaped manner. Thus configured, the wedge scanner can record the content of a partially open book. However, this solution can not prevent that damage or deterioration occurs to the book when the wedge scanner comes into contact with the pages.
Finally, the previous methods are limited to single picture of a page, which allows only a 2-dimensional analysis of the content of the page. Considering that pages of books also contain a lot of additional information in various features such as the diverse materials used (e.g. ink, gold), imprints of printing making process, various defects, and undulations of the paper, such methods do not permit a complete analysis of a page of a book from a single digital picture, which is a growing demand of libraries.
A need therefore exists to develop an apparatus for imaging a page of a book or other similar document that overcomes the deficiencies of the above mentioned apparatus.